new plants: jungle and birch trees, cactus.

Implemented Jungle and Birch trees, added Cactus, made land generation
to plants a bit more selective
merge 5415065edc6dcef32e63b1340ce313d754dda511

merge from boksee with the added trees, cactus, etc.
updated screenshot
Update README.md
readme update (2)
New TODO.md
ItemSelector.get_current_block: No longer removes blocks
That functionality split into ItemSelector.remove_current_block
Prevents player from placing blocks inside themselves
New TODO.md (2)
Merge commit '868c7e1bb3acee6982fbeff10e0e03b7e9db4494'

Conflicts:
	README.md
	TODO.md
	Thumbs.db
	blocks.py
	gui.py
	inventory.py
	main.py
	screenshot.jpg
Added experimental sound system for "breaking" wood . WARNING: Make sure that your speakers / headphones are turned off - it may play sound very loud!

You should also have AVBin library installed (http://avbin.github.com/AVbin/Download.html), which should be installed with pyglet as default.
Created proper MC-like Inventory screen.
Merge branch 'master' of git://github.com/avelanarius/Minecraft
Cleanup in gui.py.
Optimizes Model.initialize.  Before: ~ 2.2s − After: ~ 0.8s.
Merge branch 'master' of https://github.com/boskee/Minecraft
Items can now be moved between inventory and quick slots
Optimizations.  Saves ~ 0.2s on initialization.
Merge branch 'master' of git://github.com/BertrandBordage/Minecraft

Conflicts:
	gui.py
Merge branch 'master' of https://github.com/boskee/Minecraft

Conflicts:
	gui.py